50 years of Gazelle helicopters
The British Army Air Corps is the first military user of the Gazelle. More than 200 copies were used as training, communications and reconnaissance helicopters; they will remain in service until the middle of the third decade of the twenty-first century. Photo by Milos Rusecki
Last year, the 60th anniversary of the Gazelle helicopter flight was celebrated. In the late XNUMXs and into the next decade, it was one of the most modern, even avant-garde designs in its class. Innovative technical solutions set the design trends for the next decades. Today, it has been superseded by newer types of helicopters, but it is still an eye-catcher and has many fans.
In the mid-60s, the French concern Sud Aviation was already a recognized manufacturer of helicopters. In 1965, work began there on the successor to the SA.318 Alouette II. At the same time, the military put forward requirements for a light surveillance and communications helicopter. The new project, which received the initial designation X-300, was to be the result of international cooperation, primarily with the UK, whose armed forces were interested in purchasing helicopters of this category. The work was supervised by the chief designer of the company René Muyet. Initially, it was supposed to be a 4-seat helicopter with a takeoff weight of no more than 1200 kg. Ultimately, the cabin was increased to five seats, alternatively with the possibility of transporting the wounded on a stretcher, and the mass of the helicopter ready for flight was also increased to 1800 kg. A more powerful than originally planned engine model of domestic production Turbomeca Astazou was chosen as a drive. In June 1964, the German company Bölkow (MBB) was commissioned to develop an avant-garde main rotor with a solid head and composite blades. The Germans have already prepared such a rotor for their new Bö-105 helicopter. The rigid type head was easier to make and use, and the flexible laminated glass blades were very strong. Unlike the German four-bladed main rotor, the French version, abbreviated MIR, was to be three-bladed. The prototype rotor was tested on the factory prototype SA.3180-02 Alouette II, which made its first flight on January 24, 1966.
The second revolutionary solution was the replacement of the classic tail rotor with a multi-bladed fan called Fenestron (from the French fenêtre - window). It was assumed that the fan would be more efficient and with less drag, reduce the mechanical stress on the tail boom, and also reduce the noise level. In addition, it had to be safer in operation - less subject to mechanical damage and much less threatening to people in the vicinity of the helicopter. It was even thought that in flight at cruising speed, the fan would not be driven, and the main rotor torque would only be balanced by the vertical stabilizer. However, it turned out that the development of the Fenestron was much slower than the work on the airframe itself. Therefore, the first prototype of the new helicopter, designated SA.340, temporarily received a traditional three-bladed tail rotor adapted from the Alouette III.
Difficult childbirth
An instance with serial number 001 and registration number F-WOFH made its first flight at Marignane Airport on April 7, 1967. The crew consisted of renowned test pilot Jean Boulet and engineer André Ganivet. The prototype was powered by a 2 kW (441 hp) Astazou IIN600 engine. In June of the same year, he made his debut at the International Air Show in Le Bourget. Only the second prototype (002, F-ZWRA) received a large fenestron vertical stabilizer and a T-shaped horizontal stabilizer and was tested on April 12, 1968. Unfortunately, the helicopter proved to be uncontrollable and was also directionally unstable during fast level flight. The elimination of these defects took almost the entire next year. It turned out that the Fenestron should, nevertheless, work in all phases of the flight, distributing air flows around the tail. Soon, the rebuilt prototype No. 001, already with Fenestron, with the F-ZWRF registration changed once again, joined the test program. Taking into account the test results of both helicopters, the vertical stabilizer was redesigned and the horizontal tail was transferred to the tail boom, which made it possible to significantly improve directional stability. However, the rigid rotor head, ideal for the four-bladed configuration, was prone to excessive vibration in the three-bladed version. When exceeding 210 km / h during the test for maximum speed, the rotor stalled. It was only thanks to his experience that the pilot avoided the disaster. Attempts were made to correct this by increasing the stiffness of the blades, which, however, did not improve the situation. In early 1969, the decision was made to take a sensible step back by replacing the articulated rotor head with a semi-rigid design with horizontal and axial hinges and no vertical hinges. The improved main rotor was installed on the upgraded first prototype 001, and on the first production version SA.341 No. 01 (F-ZWRH). It turned out that the new, less avant-garde warhead, in combination with flexible composite blades, not only significantly improved the piloting and maneuvering characteristics of the helicopter, but also reduced the vibration level of the helicopter. First, the risk of rotor jamming is reduced.
Meanwhile, the issue of Franco-British cooperation in the field of the aviation industry was finally resolved. On April 2, 1968, Sud Aviation signed an agreement with the British company Westland for the joint development and production of three new types of helicopters. The medium transport helicopter was to be put into serial production of the SA.330 Puma, the airborne helicopter for the naval forces and the anti-tank helicopter for the army - the British Lynx, and the light multi-purpose helicopter - the serial version of the French project SA.340, for which the name was chosen on languages of both countries Gazelle. Production costs were to be borne by both parties in half.
At the same time, model samples for production vehicles were produced in the SA.341 variant. Helicopters No. 02 (F-ZWRL) and No. 04 (F-ZWRK) remained in France. In turn, number 03, originally registered as F-ZWRI, was transported in August 1969 to the UK, where it served as a production model of the Gazelle AH Mk.1 version for the British Army at the Westland factory in Yeovil. It was given the serial number XW 276 and made its first flight in England on 28 April 1970.
